Session: 8

PS8-04 | Searching for the hippocampal engram in a virtual discrimination task

Maria Sol Ramos


That memory persists after an experience suggests that an internal representation of this experience is stored in the brain and that later this representation can be reconstructed and used. This internal representation, known as the memory trace or engram, is constituted by subsets of neurons synchronously activated during learning. The dentate gyrus (DG) of the hippocampus participates in several mnemonic functions included the association of individual events with the background settings of an experience. Adult neurogenesis occurs in the DG producing different population of neurons at different stages of development during learning. We are conducting experiments training mice to perform a GO/NO GO discrimination task in a virtual reality environment. In head-fixed conditions, water restricted mice learn to drink water or not depending on the visual context presented in a virtual corridor. We show that animals reached to criterion within a few sessions and we analysed the development of distinct behavioural variables. We used cfostTA transgenic mice injected with AAV9-TRE-GFP in the DG to label activated neurons. By performing ex-vivo electrophysiological recordings, we aim to study the excitation/inhibition balance on activated and non-activated cells of expert animals. To further investigate the contribution of engram cells and adult-born neurons in this task, we are developing different transgenic mice lines to reversibly inactivate them using a DREADD approach.